A motorist travelling at a steady speed of 90 km/h covers a section of road in 25 minutes. After a speed limit is imposed he finds that when he travels at the maximum speed it takes him 5 minutes longer than before to cover the same section.Calculate the speed limit.

Question

whpalmer4 · Answer

$$d=rt$$where $d$ is distance, $r$ is rate or speed, and $t$ is time

Use that formula to find the distance traveled in 25 minutes at 90 km/h.  You'll have to convert one of those numbers to have compatible units with the other; I suggest that you change the speed to km/min by multiplying by 1 hr/60 min

Having found the distance, you can now find the speed limit with the same formula, given that the time is now 30 minutes instead of 25.